Process and appliance for projecting television pictures



N 1945.- F. E. FISCHER 2,39'1Q451 PROCESS: AND APPLIANCE FOR PROJECTING TELEVISION PICTURES Filed June 10, 1941 '4 Sheets-Sheet. 1 1

- INV ENTOR. if F/sc/zer ATTORNEYS I 3 19 45. I YF.IIE. FISCHER i 1 PROCESS AND APPLIANCE FOR .PRQJECTING TELEVISION PICTURES Filed June 10', 1941 4 sheets-sheet:

.gzsqr 70. h

INlfENTOR.

E f. F/ c/z er Patented Dec. 25, 1945 UNITED STATES PATIENT oFrlca PROCESS AND APPLIANCE FOR PROJECTIN TELEVISION PICTURES Friedrich Ernst Fischer, Zurich ,;Swltzerland Application June 10, 1941, Serial No. 397,453

lliswitzerland June 11, 1940 v I 13 Claims. It is a known method for making large television pictures to control the light of a given light source by means of a medium which is being changed point-by-point by the action of a cathode ray modulated with the television signal. Furthermore, the light of a separate light source is allowed to pass through, or to be reflected, to agreater or lesser extent at the difierent spots of the surface, depending on the extent of the change to which the surface, at a given spot, has been subjected by the cathode ray.

It has already been suggested to use as a deformable layer some crystal medium consisting picture.

For this reason, it is more advantageous to use a medium spread so as to form a flat surface, and to deform the surface of this medium directly by applying charges on to it.

Through the deformation of the surface of the medium lenses are also formed which permit the control point-by-point of the light beam originating from the light source, according to the.

brightness values of the television picture.

The use of various materials as a deformable layer is here conceivable. As the result of tests it has been found that the use of a fluid presents great advantages, in view of the fact that the surfaces of fluids can be deformed by comparatively small electrostatic forces, and that, further, fluids yield optically unobjectionable surfaces without any special auxiliary means. n the other hand the use. of fluids is not possible straight away. It is, now, advantageous to put the deformable medium under charge by applying an initial potential. This initial potential is conveniently produced by sweeping over the surface with an electron source. It is obvious that when using a fluid as medium this initial potential-should it not be applied absolutely uniformly-has as its consequence an undesirable deformation of the surface through shifting of the medium as a whole.

v Since, on the other hand, absolutely uniform initial potential is practically unattainable, undesirable deformations and consequently disturbing brighteningsof the picture are unavoidable.

In order to avoid this deformation of the whole picture surface the layer thickness of the fluid medium could be selected very thin and, consequently, due to the tenacity (viscosity) of the fluid, a shifting rendered more difllcult. Since, however, the medium is subjected for hours to the initial potential, such a means would not prevent the undesirable deformation. Moreover, the

sweeping over with the electron beam and with the light of the separate light source would warm up the medium, which is not admissible either.

According to the process of the present invention these problems'have now been solved by moving the medium. 7

By moving the medium a constant renewal is secured, and consequently the deformation of the surface as a whole rendered impossible.

Furthermore, it is possible to cool the medium after each sweeping-over of the electron beam and each projection. The motion of the medium may either be so slow that the quality of the picture will not be interfered with by the projection of the moving medium, or it could be so rapid that the velocity of the medium will correspond to the line change, so that the electron beam need not be described on to the whole picture any more, but only led along one line.

8 The appliances for carrying into effect the method outlined above consist mainly of a carrier on to which the medium is applied and which is moved at the required velocity.

In the accompanying drawings are shown, and below are described, a few constructional examples of appliances for carrying into effect the process according to the present invention.

The various drawings show in:

Fig. 1 a schematic representation of the whole arrangement;

Fig. 2 a constructional example of the moving medium carrier;

Fig. 3 a detail of Fig. 2;

Fig. 4 a second constructional example of the moving medium carrier;

Fig. 5 a section through the arrangement of Fig. 4;

Fig.6 a band-shaped medium carrier;

Fig. 7 a vertically rotating medium carrier;

Fig. 8 an arrangement in which the medium itself moves independently of any carrier;

Fig. 9 an example in which the medium is Y arranged outside the cathode ray tube; and

Fig. 10 is a quick-motion medium carrier.

In Fig. 1 the cathode ray tube is designated with I; the two electron guns 2 and 3 included in it are intended to produce cathode rays. The electron gun 2 produces the cathode ray controlled by the deflecting plates 4 and applies on to the medium 5 the charges proper in accordance with the brightness values of the television picture. The electron gun 3 merely serves to apply on to the medium a constant initial potential. 1 is the transparent moving medium carrier, of which Figs. 2-5 show various constructional examples. 3 is the separate lightsource the light rays of which fall on to the medium 5 over mirror 3, slot system Ill, lens through a transparent opening I2, and are deflected there according to the deformation of the medium. Over asec- 0nd slot system i3, lens i4, mirror 15, the light rays reach the projection screen IS. The two slot systems In and I3 are so attuned to each other that as long as the medium is undeformed no light falls on to the screen l6, since each slot of the system It corresponds to a bar of the system l3. It is only the deflection through the medium I that allows the light to pass through on to screen [6. I

Fig. 2 gives a full representation of a transparent medium carrier 1. I1 is a rotating disc on which the fluid medium is spread out in the form of a thin layer. Disc I1 is driven from motor l3 over transmission gear |3. Motor i8 further drives-in the sense indicated by arrows-over transmission gear 23 a roller 2| arranged over disc I! with a slight interval inbetween. A knife 22 is pressed against the roller 2| after the manner of a stripper. is arranged a rake 23 which is caused by eccentric 24 to move to and fro and up and down and which is supported in bearing 29. On disc i1 there is further arranged, at an interval corresponding to the layer thickness, a hollow body 25 which is cooled by a cooling liquid which enters such body by one of pipes 26 and leaves by the other of the pipes 26. 2 is the electron source of which the electron beams 21 sweep over the optically utilised area 28 of the fluid medium.

The operation of the arrangement is as follows:

Through the motion of the disc 11 the medium exposed to the electron beam 21 is removed out of its sphere of influence. The medium now gets underneath the body 25 where it is cooled. In the course of its further motion the medium finally gets underneath the rotating roller 2| which brings about the flattening of the medium, required fior the projection. I'he stripper 22 strips off the fluid, adhering to the roller 2|. For claritys sake these processes are represented schematically on Fig. 3. The fluid damming-up which takes place behind the roller 2| is designated with 30.

The rake 23 simultaneously moving to and fro and up and down is intended to distribute uniformly over the whole width of the disc II the accumulation of fluid behind the roller 2|. It will be understood that the carrier moves at such a relatively low speed that the projected picture does not become blurred.

In Figs. 4 and 5, contrary to the example according to Fig. 2, the flattening of the fluid is effected-instead of by a, rotating roller-by a sharp knife 3|. The knife 3| is fastened to a body 32 which covers up one half of the disc I! and, similarly to body 25 in the example acpliance 23 body 32 also includes a canal 33 running across the disc l1 and serving to take up the fluid 34 dammed up in front, of the knife 3| and to lead it to the other side of the disc, where stripped down to the desired layer thickness and Directly in front of roller 2| cording to Fig. 2, is'arranged over the disc I1,

flattened. The fluid layer thus formed on the carrier 35 is used for the projection and comes thereupon over guide rollers 4| into the trough 42 in which is arranged the roller 31 on to which the carrier 35 is wound up.

In Fig. 'I the disc I! rotates vertically and partly dips into a trough 43 in which is the fluid serving to form the layer, Through the rotation of the disc the fluid is carried out of the trough 43 and, under the action of the roller 44, stripped down to the desired layer thickness and flattened. In order to prevent the formation on the rear of the disc I! of an interfering uneven layer, a roller .45 must also be provided there so as to strip of! the medium entirely.

Fig. 8 is a section through an arrangement in which the medium carrier 46 is stationary, while the fluid 41 flows over it in a layer of a given thickness and with the desired velocity which may be regulated by the inclination of the plane on which the fluid flows down. The trough 48 collects the fluid, while trough 49 serves as storage tank. It is of course possible -in order to secure a continuous workingto pump continuously the fluid out of trough 48 into trough 43 and, if required, to have it cooled in transmission.

The arrangements shown in Figs. 2-8 are only a few simple constructional examples which may serve to carry into efiect the process according to the invention. These examples may, of course, be added to by any expert without any difliculty and without departing from the scope of the invention.

Fig. 9 shows an example in which the medium is subjected to a rapid motion so that a movement of the cathode ray in the direction of the picture is no longer needed. E

The cathode ray tube is designated with I; it again includes two electron guns 2 and 3 for producing cathode rays, The electron gun 2 produces the cathode ray which, controlled by the deflecting spools 4, applies the charge distribution proper on the medium. The electron gun 3 serves to apply a continuous charge or to produce a constant initial potential on to the medium, and may be built up in such a way that an incandescent filament will be portrayed electron-optically on the medium. The cathode ray tube is provided with an opening 5!] closed by a thin metallic foil and constituting the so-called Lenard window. The Lenard window is arranged immediately over a carrier 5| in the shape of an endless band stretched on, and driven by, rollers 52 and 52a. Rollers 52 and 52a run in 'a trough 53 filled with the medium, for which a fluid has been selected in this case. Through the clockwise rotation of rollers 52 and 53a the medium adhering to carrier 5| is carried along, superfluous medium being stripped oil by the stripping roller 55. The carrier is transparent.

The light ray 56 now throws its light rays on to the mirror 53 over condenser 51 and diaphragm ll. Mirror 69 throws the lighton to mirror 6| over objective in through the deforming medium. In the further ray path there is provided again a diaphragm 62, an objective 63 and a "Mechau mirror wheel for the purpose of optical compensation. From the "Mechau" mirror wheel the picture is thrown on to the projection screen 66 over a mirror 65. Over the medium stretched out fiat there is a screen 61 with a window 68' on to which potential is applied.

It may further be mentioned that the diaphragms 68 and 62exactly as' in Fig. 1--are so selected that with undeformed medium no light falls on to the projection screen, e. g. the slots of the diaphragm 58 are portrayed on the bars of the diaphragm 62.

The operation of this arrangement may be summed up as follows:

The cathode ray tube l describes each time through deformation of the medium placed below the Lenard window a line modulated according to the brightness distribution of the television picture.

The medium moves on until it arrives in the ray path of the light source 56, where the television picture constituted on the medium in the shape of a deformation is thrown on to the pro- Jection screen 66 over mirror 6|, diaphragm 62, objective 63, mirror wheel 64, mirror 65.

Fig. 10 shows a constructional example in which the motion mechanism and the medium itself are arranged within the cathode ray tube. The cathode ray tube I again includes two electron guns 2 and 8 for producing cathode rays, the electron gun 3 again serving to produce a constant initial potential. Inside the cathode ray tube I is provided a drum 69 dipping into the bath l6 and carrying along the medium in its clockwise rotation. Inside the drum 69 is arranged a mirror 59 on to which falls the light of the light source 56 arranged laterally, over condenser 51 and diaphragm 58, which mirror 59 in its turn throws the impinging light rays on to the diaphragm 62 and lens 63, over objective 66 through the medium, from where, as in the constructional example according to Fig. 9, the picture reaches the projection screen 66 over the Mechau mirror wheel 64 and the mirror 65.

The scope of the invention is of course by no means exhausted by the constructional examples shown; on the contrary, numerous constructional alternatives are conceivable. For instance, in place of the fiuid medium, a medium consisting of gum could be used and the band or drum surface now built up as medium carrier could then themselves be built up as deformable medium. Furthermore, in the constructional example according to Fig. 10, the appliances for producing the electron beam could also be arranged inside the drum, the medium, in such a case, adhering to the inner wall of the drum as a consequence of the rotary motion of the drum.

Finally, .the appliance for producing a constant initial potential on the medium need not necessarily be arranged within the cathode ray'tube. On the contrary, the same purpose could also be fulfilled by means of an incandescent filament arranged outside the cathode ray tube immediately over the medium and extending over one.

line.

What I claim and desire to secure by Letters by means of a cathode ray tube and a separate light source, comprising, in combination with the cathode ray tube and separate source of light, a moving liquid film in the path of the cathode and light rays and adapted to be deformed by the cathode ray into differently refracting areas in accordance with the changing characteristics of the cathode ray, and means for setting said film into motion. a

2. Apparatus according to claim 1, including a carrier for the film provided with a cooling appliance by means of which, after each projection, the medium is cooled down to the required temperature.

3. Apparatus according to claim 1, wherein said means comprises a moving carrier for the film, and astripping element arranged to strip the liquid down to a predetermined film thickness andfiattening the film on the carrier.

4. Apparatus according to claim 1, wherein said means includes a carrier for the film, and wherein the carrier with the liquid film thereon is arranged within the cathode ray tube.

5. Apparatus according to claim 1, wherein said means includes a carrier for the film, and wherein the carrier is in the form of a moving band.

6. Apparatus according to claim 1, wherein said means includes a carrier for the film, and wherein the carrier is a drum.

7. Apparatus according to claim 1, wherein said means includes a carrier for the film, and wherein the carrier is in the form of a disc.

8. Apparatus for producing a television picture by means of a cathode ray tube and a separate light source, comprising, in combination with the cathode ray tube and separate source of light, means providing an electronically deformable, viscous surface in the path of the cathode and light rays and adapted to be deformed by the cathode ray into differently refracting areas in accordance with the changing characteristics of the cathode ray, means for setting said viscous surface into motion to present continuously fresh surface to the deforming action of the cathode ray, and a device for subjecting the viscous surface to an initial electrostatic potential.

9. Apparatus according to claim 1 wherein the carrier is in the form of a horizontally disposed transparent disc arranged inside the cathode tube, the means for setting the film into motion comprising a motor connected with the disc to rotate the same about a central vertical axis, at a relatively low speed, a viscous liquid film being disposed on said disc, and a knife mechanism for skimming the film to a uniform thickness.

10. Apparatus for producing a television picture by means of a cathode ray tube and a separate light source, comprising, in combination with the cathode ray tube and separate source of light,

separate light source to the so deformed area ofthe medium and projecting the modulated light beam upon the screen, and means whereby the deformed area of the medium is caused to move progressively out of the field of the cathode and light rays, whereby fresh deformable surface is the deformable medium is a viscous liquid and. is suiflciently fluid to enable it to flow, the means providing an electronically deformable viscous surface including a flat carrier and mechanism for spreading the viscous materially uniformly over the area of the carrier associated with the fleld of the cathode ray.

13. Apparatus according to claim 10 wherein the deformable medium is a viscous fluid and wherein the lastmentioned means is of a nature to cause themedium to move at a velocity corresponding to thespeed of line change, the cathode ray tube including mechanism for leading the cathode ray along only one line, and a cooling device for cooling the viscous fluid medium after it has left the field of the cathode ray.

FRIEDRICH ERNST FISCHER. 

